This invention relates to improvements in the means regulating the air intake and the exhaust gas emission from reciprocal, internal combustion engines. Specifically, the improvements relate to the modification in the design of valve systems for recently introduced quad-engines, which are multi-cylinder engines in which each cylinder is serviced by four valves. While the improvements herein have application to engines including more than four valves as have been proposed in certain Japanese designs, the four valve engine provides the necessary flexibility to incorporate the design modifications herein proposed.
The four valve engine, with two intake and two exhaust valves, was developed to increase the available surface area for rapid intake and exhaust of maximized volumes of air and combustion gases to and from the combustion chamber during high speed operation of compact, turbo-charged engines having a minimum number of cylinders. The popular quad-four engine is designed as a four cylinder engine with each cylinder serviced by four valves and designed for an optimum power output matching that of a comparable V--8 engine. While the gas flow design of a four valve engine provides maximum power at high operating speeds, it has been found that the developed torque at low r.p.m. is disappointing. At low r.p.m. the cylinders tend to be overcharged with air and overevacuated resulting in fuel loss and inadequate combustion of excessively lean fuel-air mixtures. When the four-valve per cylinder engine is compared with two-valve per cylinder engine, the two-valve engine has exhibited superior performance at low engine operating speeds, developing better torque and mileage than that of the state of the art quad-engine.
In developing a reciprocal engine suitable for automotive use with low emissions and high efficiency the engine must satisfy a customer who dreams of sporting excellence coupled with the necessity of city driveability. To achieve this dream the engine must have an optimized torque that develops power not only during high speed freeway operation, but during the day to day., stop and go traffic of the urban commute.
The solutions provided by this invention enable a four cycle, cam operated, four-valve per cylinder engine to continuously adjust the air intake and exhaust flow through the engine in response to electronically sensed operating conditions. Using the means devised, the four-valve engine can be operated with each valve operating independently according to timing and displacement such that the optimized gas flow conditions match the vehicle road conditions and driver demand. By use of the particular components selected to accomplish the variable character of valve operation, the response to electronically sensed operating conditions can be immediate and accomplished by use of component having low inertia and high-speed, electronic actuation.
The improved gas flow means devised and described in this invention can be incorporated into a new engine or can be adapted for use in existing engines by incorporation in a replacement head. The means devised can be adapted to two-cycle engines and other cam operated engines, where variations in the effective amplitude and period of the cam are desired.